Medical and surgical instruments are commonly packed in a package which allows the passage of gases for sterilization purposes. For example, they may be sealed in a paper package which is then placed in an atomosphere of ethylene oxide under pressure. The gas passes through the paper into the package to sterilize the contents thereof, and then the package is left in the air, generally at atmospheric pressure, to vent the sterilizing gas. Because of the toxic nature of ethylene oxide when introduced into the human body it is necessary that the venting process should be substantially completed before the contents of the package are used. This requirement necessitates the relatively free passage of gas through the walls of the package.
A serious disadvantage of such paper packages is that they are susceptible to damage; such damage may be caused by contact with a sharp object or by rough handling, or the contents of the package may rupture the walls, particularly when the packed instrument includes a needle. Of course, when a sterilized package is damaged, the ingress of bacteria becomes a possibility, and the sterility of the contents of the package can no longer be assumed.
In an attempt to alleviate the problem of damage, rigid or semi-rigid packages have been proposed. A typical example is a tubular package made of cellulose acetate. Such packages have the advantage that they allow observation of the contents of the package. However, owing to the low rate of diffusion of sterilizing gas through the walls of such packages, it is necessary to provide a filter element in a wall to allow the passage of gas, while preventing the entry of bacteria. The use of filter elements has again led to problems in preventing damage and maintaining sterility. An example of a prior proposal is a tubular package provided at one end with a surgical cotton plug. Such plugs are particularly susceptible to damage and, furthermore, if they are moistened they become ineffective in preventing the ingress of bacteria. Other prior proposals include the use of a disc of a thin, porous plastic film or other thin filter material, heat-sealed onto the end of a tubular package. The strength of such filters is inadequate and, furthermore, heat-sealing around a circular line has proved unreliable and contamination of the contents of the package has occurred. There is, moreover, no simple way of checking the integrity of such a seal.